Many people use mobile stations (e.g. cell phones and personal digital assistants (PDAs)) to communicate with cellular wireless networks, which provide communication services such as voice, text messaging, and packet-data communication. These mobile stations and networks typically communicate with each other over a radio frequency (RF) air interface according to one or more wireless protocols (e.g. CDMA (Code Division Multiple Access), EV-DO (Evolution Data Optimized), etc.). Mobile stations typically conduct communications with these networks via one or more base transceiver stations (BTSs), which send communications to and receive communications from mobile stations over the air interface.
Each BTS is typically connected with a network entity known as a base station controller (BSC), which controls one or more BTSs and acts as a conduit with one or more switches or gateways, such as a mobile switching center (MSC) and/or a packet data serving node (PDSN), which may then interface with one or more signaling and/or transport networks. As examples, an MSC may interface with the public switched telephone network (PSTN), while a PDSN may interface with one or more core data networks and/or the Internet. As such, mobile stations can typically communicate over the one or more signaling and/or transport networks from anywhere inside the coverage area of one or more BTSs, via the BTS(s), a BSC, and a switch or gateway.
Mobile stations and base stations (i.e. BTSs or BTS/BSC combinations) conduct these communications over frequencies known as carriers, each of which may actually be a pair of frequencies, with the base station transmitting to the mobile station on one frequency (i.e. the forward link), and the mobile station transmitting to the base station on the other (i.e. the reverse link). This is known as frequency division duplex, and an instance of a carrier in a coverage area referred to as a sector may be known and referred to herein as a sector-carrier.